For a long time it has been known that aliphatic peroxycarboxylic acids (aliphatic percarboxylic acids) can be produced by reaction of the aliphatic carboxylic acid in question with hydrogen peroxide in the presence of sulfuric acid, see, e.g., Swern, Chemical Reviews, Vol. 45 (1949) page 5; Silbert, et al, J. Org. Chem. Vol. 27 (1962), pages 1336-1342.
While this process is successful for obtaining aliphatic peroxycarboxylic acids, repeated attempts to use it for the reaction of aromatic acids with hydrogen peroxide did not lead to the desired results. Either there resulted decarboxylation or sulfonation/hydroxylation of the aromatic ring or total oxidative decomposition, see Silbert, et al, loc. cit. page 1337; Silbert U.S. Pat. No. 3,143,562 and related Swern German AS 1155113 as well as related Koninklijke British Pat. No. 930,056, Melthodicum Vol. 5 (1975) C-O-Verbindungen, page 739; Berkowitz U.S. Pat. No. 4,147,720.
Those skilled in the art until recent times were under the impression that sulfuric acid was unsuited as a solvent or even only as a catalyst acid for the production of aromatic peroxycarboxylic acids (aromatic percarboxylic acids).
In order to meet these difficulties the system "aromatic carboxylic acid-hydrogen peroxide-sulfuric acid" was replaced by the system "aromatic acid-hydrogen peroxide-methanesulfonic acid", i.e. in place of sulfuric acid there was used methanesulfonic acid, see Silbert, loc. cit.
However, in contrast to sulfuric acid, methane sulfonic acid is not an easily accessible industrial based chemical and thereby places an unlimited burden for carrying out the process industrially.
Since the aromatic percarboxylic acids also are included in the important oxidizing agents and e.g. play a roll in epoxidation and also in the oxidation of sulfides or tert. amines as well as bleaching and disinfecting agents, it has been very strongly desired to have a process which permits the production of aromatic percarboxylic acids without the use of industrially very expensive materials.
The purpose of the invention therefore is the development of a process for the production of aromatic percarboxylic acids using readily available industrial materials.